This application is related to Japanese application No. HEI 11(1999)-265640 filed on Sep. 20, 1999 whose priority is claimed under 35 USC xc2xa7 119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to an information recording medium and an information recording and reproducing slider and, more particularly, to an information recording medium which is improved in recording/reproducing characteristics according to which information is magnetically recorded and reproduced, as well as to an information recording and reproducing slider suited to recording and reproduction of information on and from the information recording medium.
2. Description of Related Art
Optical recording media such as DVDs and magnetic recording media such as HDDs have been known and have gained popularity as information recording media. In addition since it has been desired to enhance the recording density of information, research has been made into magneto-optical (MO) recording media in which the merits of optical recording media and the merits of magnetic recording media are combined.
According to an information recording/reproducing method of magnetically detecting information recorded on a magnetic material of the magnetic recording medium or the magneto-optical recording medium among the above-described recording media, as the result of more advanced research, it has become possible to record information at ultrahigh density. It has presently been proved that there is a possibility of ultrahigh-density recording exceeding 10 Gbits/(inch)2.
A polycrystalline magnetic material, such as Co77Cr15Pt6Ta2, which has an easy axis of magnetization in an in-plane direction is normally used as such a magnetic material.
Use of a perpendicular magnetization film made of a rare earth-transition metal amorphous alloy as the magnetic material of the magnetic recording medium is described in Japanese Unexamined Patent Publication No. SHO58(1983)-165306. This rare earth-transition metal amorphous alloy is used as a magnetic material for magneto-optical recording media, and magneto-optical recording media having a laminated body of rare earth-transition metal amorphous alloys having different magnetic characteristics have recently been described in Japanese Unexamined Patent Publication Nos. HEI5(1993)-217226, HEI5(1993)-325283, SHO63(1988)-302448 and the like.
Among them, Japanese Unexamined Patent Publication No. SHO63(1988)-302448 describes a magneto-optical recording medium having a laminated body in which a so-called rare earth (RE) rich film
More specifically, a description is made of a magneto-optical recording medium in which a TbFeCo film having a larger Kerr rotation angle is used as the TM rich film and a TbFeCo film capable of providing a large signal level ({square root over (R)}xe2x80xa2xcex8: R=reflectance, xcex8=Kerr rotating angle) is sued as the RE rich film, and both films are exchange-coupled to each other. It is stated that this medium has advantages in that a large SNR can be obtained because a rise in noise level can be restrained, and writing energy can be made small. In other words, it can be considered that if the medium described in this publication is used as a medium such as a MO disk, recording noise can be reduced while retaining a large magneto-optical effect.
To improve the recording density to a further extent, noise which occurs in an information recording medium needs to be reduced to a further extent. To this end, the grain size of magnetic grains (crystal grains) must be made approximately 10 nm.
However, if the grain size of the crystal grains of the above-described polycrystalline magnetic material is made approximately 10 nm, the resulting magnetic domains (recorded bits) become thermally unstable at, in particular, the interfaces of the crystal grains. This fact causes problems that noise is produced in the information recording medium, recorded information disappears and the like. In particular, the adoption of such minute magnetic grains causes the problem that the coercive force of the information recording medium becomes lower with a temperature rise (normally, the temperature inside a drive in use becomes approximately 65xc2x0 C.).
In addition, it cannot be said that the medium described in the above-cited Japanese Unexamined Patent Publication No. SHO63(1988)-302448 is appropriate for a method of reproducing magnetic flux. For example, in Example 1 of this publication, a description is made of a medium formed of a laminated body of a magnetic film of Hc=2 kOe (thickness=20 nm) and a magnetic film of Hc=10 kOe (thickness=60 nm). This medium has the coercive force substantially larger than that recordable by a normal magnetic head, and thus the recording is difficult.
In addition, it is in general necessary that the magnetization of a medium be large to an extent detectable by a magnetic head.
In the case of the medium of the above-cited publication, it is inferred that the magnetization of the magnetic film of Hc=2 kOe is comparatively large and the magnetization of the magnetic film of Hc=10 kOe is comparatively small. Total magnetization is the sum of the values of magnetization of magnetic films which constitute a medium. However, in the case of the medium of the above-cited publication, since the film having a larger magnetization is thin, its total magnetization is very small and the medium does not emit magnetic flux to the outside, so that detection by a magnetic head is difficult.
According to the present invention, there is provided a first information recording medium comprising an information recording film formed on a base on which regular depressions and projections having Ra of 0.1 to 1.5 nm or period of 10-40 nm have been formed, the information recording film containing as a major component a rare earth-transition metal amorphous alloy capable of magnetically reproducing a recorded information.
In addition, according to the present invention, there is provided a second information recording medium comprising an information recording film made of an exchange-coupled multilayer film capable of magnetically reproducing a recorded information, wherein the exchange-coupled multilayer film has a coercive force which is not substantially changed at a temperature ranging from room temperature to approximately 65xc2x0 C., the product of 55 Gauss xcexcm or more of a remnant magnetic flux density and a film thickness, and includes at least a transition metal-rich rare earth-transition metal amorphous alloy layer and a rare earth-rich rare earth-transition metal amorphous layer.
Furthermore, according to the present invention, there is provided a slider for recording and reproducing information used for recording or reproducing on or from above information recording medium, the slider comprising a light irradiating means, a recording head and a magnetic reproducing head that are integrated, the light irradiating means being located ahead of the recording head and the magnetic reproducing head in the direction of information recording and reproducing.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.